King announced his retirement last month and a host of rivals, many of them better known in America, were in the running to replace him on his nightly interview slot. They included American Idol host Ryan Seacrest and CBS News presenter Katie Couric.

Morgan, 45, who celebrated his marriage to Daily Telegraph journalist Celia Walden at a lavish party last month, is believed to have impressed CNN executives with his interviewing style.

Talks were complicated by Morgan's commitments to NBC. His NBC contract prevented him from taking on extra work that clashed with the show, but this has now reportedly been resolved.

Many of the interviews for the CNN show, broadcast in the key 9pm slot on the US east coast, are recorded and Morgan will still have time to star in the NBC talent contest.

He is also expected to continue to make one-off shows for ITV as well as another two series of interview show Piers Morgan's Life Stories, each running to 12 programmes.